Food and drink packaging frequently demands a high barrier effect with respect to gases, water vapor and flavors. For this reason, use is usually made of polypropylene films which have been metallized or have been coated with polyvinylidene chloride (PVDC). However, metallized polypropylene films are not transparent and are therefore not used in cases where the view of the contents is likely to have added promotional effect. Although films coated with PVDC are transparent, the coating, like the metallizing, takes place in a second operation which makes the packaging markedly more expensive. Ethylene-vinyl alcohol copolymers (EVOH) likewise exhibit a strong barrier effect. However, films modified with EVOH are particularly highly moisture-sensitive, and this limits their range of applications. In addition, because of their poor mechanical properties they have relatively high thickness or have to be laminated with other materials at high cost, and they are also difficult to dispose of after use. Some raw materials, furthermore, have not been approved by the authorities or are unsuitable for producing food and drink packaging.
It is therefore an object of the present invention to provide a transparent, biaxially oriented polyester film which has a high oxygen barrier and at least one additional functionality, and which can be produced simply and cost-effectively, has the good physical properties of the known films and does not give rise to disposal problems.